NuGet targeting x86, x64 and AnyCPU in one Package

Since I was spending way to much on time on the following question, I wanted to share my results with you:

NuGet allows to target quite a lot of different setups, but when it comes to some advanced stuff, It's documentation isn't great. There is also quite a lot of different stuff floating around but it's all a big mess.

So I was stuck with this: How do I include a x86, x64 and Any CPU build with different target versions in just a single package?

There are two existing SO-answers regarding this. Both of them lack a few details.

It's actually quite simple. At least, if you've spend around 5 hours on this.

1. Your files need to be placed in build\{target framework version}\{architecture}

2. You'll need to add a .props file to include your lib's. This file should contain following content:

    <?xml version="1.0" encoding="utf-8"?>
    <Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
      <ItemGroup>
          <Reference Include="MyDll">
              <HintPath>$(MSBuildThisFileDirectory)$(Platform)\MyDll.dll</HintPath>
          </Reference>
       </ItemGroup>
    </Project>
   

   make sure to replace the MyDll with your package and .dll name!*

   It has to be saved in every build/{target framework version} folder and has to use the name MyDll.props. Its final path should look something like this: build/net452/MyDll.props. You'll need to place it in every build/{target framework version} directory. This needs to be done so that NuGet stops being annoying and to get it to include our .props file. Sadly, it's not possible to include it only once in the build/ folder (In theory, yes! In practice, it doesn't work).

3. If you want to get rid of the warning WARNUNG: NU5127: This package does not contain a lib/ or ref/ folder, and will therefore be treated as compatible for all frameworks. Since framework specific files were found under the build/ directory for net452, consider creating the following empty files to correctly narrow the compatibility of the package:
-lib/net452/_._, You'll need to add an empty file with the name _._ in every lib\{target framework version} directory.

Final structure:

Your assembled NuGet package should look like this:

{root}/
  build/
    net452/
      MyDll.props
      AnyCPU/
        MyDll.dll
        MyDll.xml
        MyDll.pdb
      x86/
        MyDll.dll
        MyDll.xml
        MyDll.pdb
      x64/
        MyDll.dll
        MyDll.xml
        MyDll.pdb            
    netstandard2.1/
      MyDll.props
      AnyCPU/
        ...
      .../
  lib/
    net452/
      _._
    netstandard2.1/
      _._

Example .nuspec

<package xmlns="http://schemas.microsoft.com/packaging/2010/07/nuspec.xsd">
    <metadata minClientVersion="3.2">
        ...
    </metadata>
    <files>
		<!-- .NETFramework 4.5.2 -->
		<file src="LSDOTNETCORE.props" target="build\net452" />
        <file src="_._" target="lib\net452" />
	
        <file src="Build\AnyCPU\Release\net452\LSDOTNETCORE.dll" target="build\net452\AnyCPU" />
        <file src="Build\AnyCPU\Release\net452\LSDOTNETCORE.xml" target="build\net452\AnyCPU" />
        <file src="Build\AnyCPU\Release\net452\LSDOTNETCORE.pdb" target="build\net452\AnyCPU" />	
		
        <file src="Build\x86\Release\net452\LSDOTNETCORE.dll" target="build\net452\x86" />
        <file src="Build\x86\Release\net452\LSDOTNETCORE.xml" target="build\net452\x86" />
        <file src="Build\x86\Release\net452\LSDOTNETCORE.pdb" target="build\net452\x86" />
		
        <file src="Build\x64\Release\net452\LSDOTNETCORE.dll" target="build\net452\x64" />
        <file src="Build\x64\Release\net452\LSDOTNETCORE.xml" target="build\net452\x64" />
        <file src="Build\x64\Release\net452\LSDOTNETCORE.pdb" target="build\net452\x64" />	
		
		<!-- .NET-Standard -->
		<file src="LSDOTNETCORE.props" target="build\netstandard2.1" />
        <file src="_._" target="lib\netstandard2.1" />
	
        <file src="Build\AnyCPU\Release\netstandard2.1\LSDOTNETCORE.dll" target="build\netstandard2.1\AnyCPU" />
        <file src="Build\AnyCPU\Release\netstandard2.1\LSDOTNETCORE.xml" target="build\netstandard2.1\AnyCPU" />
        <file src="Build\AnyCPU\Release\netstandard2.1\LSDOTNETCORE.pdb" target="build\netstandard2.1\AnyCPU" />	
		
        <file src="Build\x86\Release\netstandard2.1\LSDOTNETCORE.dll" target="build\netstandard2.1\x86" />
        <file src="Build\x86\Release\netstandard2.1\LSDOTNETCORE.xml" target="build\netstandard2.1\x86" />
        <file src="Build\x86\Release\netstandard2.1\LSDOTNETCORE.pdb" target="build\netstandard2.1\x86" />
		
        <file src="Build\x64\Release\netstandard2.1\LSDOTNETCORE.dll" target="build\netstandard2.1\x64" />
        <file src="Build\x64\Release\netstandard2.1\LSDOTNETCORE.xml" target="build\netstandard2.1\x64" />
        <file src="Build\x64\Release\netstandard2.1\LSDOTNETCORE.pdb" target="build\netstandard2.1\x64" />		
    </files>
</package>